Catheter including surface-treated structural support member

ABSTRACT

In some examples, a catheter includes an inner liner, an outer jacket, and a structural support member positioned between at least a portion of the inner liner and at least a portion of the outer jacket. A surface of at least a portion of the structural support member is surface treated to increase an adhesion of the surface to at least one of the inner liner or the outer jacket. Examples surface treatments include physical treatments, chemical treatments, coating treatments, and combinations thereof. In some instances, the at least one portion of the structural support member is a relatively high density portion.

TECHNICAL FIELD

This disclosure relates to medical catheters and methods of making thesame.

BACKGROUND

A medical catheter defining at least one lumen has been proposed for usewith various medical procedures. For example, in some cases, a medicalcatheter may be used to access and treat defects in blood vessels, suchas, but not limited to, lesions or occlusions in blood vessels.

SUMMARY

In some aspects, this disclosure describes example catheters withincreased adhesion between a structural support member, such as a coilor a braid, and an inner liner and/or outer jacket, and methods offorming catheters.

In some examples described herein, a catheter includes an inner liner,an outer jacket, and a structural support member positioned between atleast a portion of the inner liner and at least a portion of the outerjacket. Prior to forming the catheter, the structural support member issurface treated by at least applying a surface treatment to a surface ofat least a portion of the structural support member, such as an innerand/or outer radial surface. As a result of one or more of these surfacetreatments, the surface of the structural support member has increasedadhesion to the inner liner and/or the outer jacket. Surface treatmentscan include physical treatments, such as roughening to increase aroughness and/or surface area of the structural support member; chemicaltreatments, such as functionalization to increase a charge or generatereactive moieties on the structural support member; coating treatments,such as coating application to add reactive moieties to the structuralsupport member; or any combinations of physical, chemical, coating, orother treatments.

In some examples, the surface treatment can be applied to particularportions of, or in varied amounts to, the structural support member toselectively reinforce portions of the structural support member that maybe relatively susceptible to displacement within the catheter (e.g.,higher density portions of the structural support member). In thesevarious ways, catheters described herein may exhibit increased adhesionbetween the surface treated structural support member and an inner linerand/or outer jacket compared to catheters that do not include a surfacetreated structural support member.

Clause 1: In some examples, a catheter includes an inner liner, an outerjacket, and a structural support member positioned between at least aportion of the inner liner and at least a portion of the outer jacket,wherein a surface of at least a portion of the structural support memberis surface treated to increase an adhesion of the surface to at leastone of the inner liner or the outer jacket.

Clause 2: In some examples of the catheter of clause 1, the structuralsupport member is surface treated on an inner radial surface of thestructural support member without being surface treated on an outerradial surface of the structural support member.

Clause 3: In some examples of the catheter of clause 1, the structuralsupport member is surface treated on an outer radial surface of thestructural support member without being surface treated on an innerradial surface of the structural support member.

Clause 4: In some examples of the catheter of any of clauses 1-3, thesurface of at least the portion of the structural support memberincludes a surface roughness greater than about 2 microns Ra.

Clause 5: In some examples of the catheter of any of clauses 1-3, thesurface of at least the portion of the structural support member iscovalently bonded to at least one of the inner liner or the outerjacket.

Clause 6: In some examples of the catheter of any of clauses 1-3,wherein the surface of at least the portion of the structural supportmember comprises a coating covalently bonded to at least one of theinner liner or the outer jacket.

Clause 7: In some examples of the catheter of any of clauses 1-3, thestructural support member comprises a coiled structural support member.

Clause 8: In some examples of the catheter of clause 7, a first portionof the coiled structural support member has a first coil pitch and asecond portion of the coiled structural support member has a second coilpitch that is less than the first coil pitch.

Clause 9: In some examples of the catheter of clause 8, the surface thatis surface treated includes a first surface of the first portion of thecoiled structural support member, and wherein a second surface of thesecond portion of the coiled structural support member is not surfacetreated.

Clause 10: In some examples of the catheter of clause 8 or 9, thesurface that is surface treated comprises a first surface of the firstportion of the coiled structural support member, the first surfacehaving a first surface roughness, and wherein a second surface of thesecond portion of the coiled structural support member has a secondsurface roughness that is less than the first surface roughness.

Clause 11: In some examples of the catheter of any of clauses 8-10,wherein a shear strength of the first portion is greater than abouttwice a shear strength of a structural support member that does notinclude the surface treatment.

Clause 12: In some examples of the catheter of clause 7, a first portionof the coiled structural support member has a first diameter and asecond portion of the coiled structural support member has a seconddiameter that is greater than the first diameter.

Clause 13: In some examples of the catheter of any of clauses 1-3, thestructural support member comprises a braided structural support member.

Clause 14: In one example, a catheter includes an inner liner, an outerjacket, a support layer positioned between at least a portion of theinner liner and at least a portion of the outer jacket, and a structuralsupport member positioned between at least a portion of the inner linerand at least a portion of the outer jacket, wherein a surface of atleast a portion of the structural support member is surface treated toincrease an adhesion of the surface to at least one of the inner liner,the outer jacket, or the support layer.

Clause 15: In some examples of the catheter of clause 14, at least aportion of the support layer is positioned between the structuralsupport member and the outer jacket.

Clause 16: In some examples of the catheter of clause 14 or 15, thesurface of at least the portion of the structural support member iscovalently bonded to at least one of the inner liner, the outer jacket,or the support layer.

Clause 17: In some examples of the catheter of clause 14 or 15, thesurface of at least the portion of the structural support membercomprises a coating covalently bonded to at least one of the innerliner, the outer jacket, or the support layer.

Clause 18: In some examples of the catheter of any of clauses 14-17, thestructural support member comprises a coiled structural support member,and a first portion of the coiled structural support member has a firstcoil pitch and a second portion of the coiled structural support memberhas a second coil pitch that is less than the first coil pitch.

Clause 19: In some examples of the catheter of clause 18, the surfacethat is surface treated includes a first surface of the first portion ofthe coiled structural support member, and wherein a second surface ofthe second portion of the coiled structural support member is notsurface treated.

Clause 20: In some examples of the catheter of clause 18 or 19, thesurface that is surface treated includes a first surface of the firstportion of the coiled structural support member, the first surfacehaving a first surface roughness, and a second surface of the secondportion of the coiled structural support member has a second surfaceroughness that is less than the first surface roughness.

Clause 21: In one example, a method for manufacturing a catheterincludes applying a surface treatment to a surface of at least a portionof a structural support member, positioning the structural supportmember around an inner liner, and positioning an outer jacket around thestructural support member and the inner liner.

Clause 22: In some examples of the method of clause 21, applying thesurface treatment comprises applying the surface treatment to an innerradial surface of the structural support member without substantiallyapplying the surface treatment to an outer radial surface of thestructural support member.

Clause 23: In some examples of the method of clause 21, applying thesurface treatment comprises applying the surface treatment to an outerradial surface of the structural support member without substantiallyapplying the surface treatment to an inner radial surface of thestructural support member.

Clause 24: In some examples of the method of any of clauses 21-23,applying the surface treatment comprises roughening the surface of atleast the portion of the structural support member to increase a surfaceroughness of the surface.

Clause 25: In some examples of the method of clause 24, the surface ofat least the portion of the structural support member includes a surfaceroughness greater than about 2 microns Ra.

Clause 26: In some examples of the method of any of clauses 21-23,applying the surface treatment comprises chemically treating the surfaceof at least the portion of the structural support member to increase acharge of the surface.

Clause 27: In some examples of the method of any of clauses 21-23,applying the surface treatment comprises chemically treating the surfaceof at least the portion of the structural support member tofunctionalize the surface with reactive moieties.

Clause 28: In some examples of the method of any of clauses 21-23,applying the surface treatment includes coating the surface of at leastthe portion of the structural support member with a reactive layer withreactive moieties.

Clause 29: In some examples of the method of any of clauses 21-23, thestructural support member includes a coiled structural support member.

Clause 30: In some examples of the method of clause 29, a first portionof the coiled structural support member has a first coil pitch and asecond portion of the coiled structural support member has a second coilpitch that is less than the first coil pitch.

Clause 31: In some examples of the method of clause 30, applying thesurface treatment comprises applying the surface treatment to a firstsurface of the first portion of the coiled structural support member andrefraining from applying a second surface treatment to a second surfaceof the second portion of the coiled structural support member.

Clause 32: In some examples of the method of clause 30, applying thesurface treatment includes roughening a first surface of the firstportion of the coiled structural support member to a first surfaceroughness and roughening a second surface of the second portion of thecoiled structural support member to a second surface roughness that isless than the first surface roughness.

Clause 33: In some examples of the method of clause 30, applying thesurface treatment comprises chemically treating a first surface of thefirst portion of the coiled structural support member to a first chargeand chemically treating a second surface of the second portion of thecoiled structural support member to a second charge that is less thanthe first charge.

Clause 34: In some examples of the method of clause 29, a first portionof the coiled structural support member has a first diameter and asecond portion of the coiled structural support member has a seconddiameter that is greater than the first diameter.

Clause 35: In some examples of the method of clause 21, the structuralsupport member includes a braided structural support member.

The examples described herein may be combined in any permutation orcombination.

The details of one or more aspects of the disclosure are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the techniques described in this disclosurewill be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of an example catheter, which includes acatheter body and a hub.

FIG. 2 is a conceptual cross-sectional view of a part of the catheterbody of FIG. 1, where the cross-section is taken through a center of thecatheter body and along a longitudinal axis of the catheter body.

FIG. 3 is a conceptual cross-sectional view of a part of a catheter bodyincluding a coiled structural support member, where the cross-section istaken through a center of the catheter body and along a longitudinalaxis of the catheter body.

FIG. 4 is a conceptual cross-sectional view of a part of a catheter bodyincluding a braided structural support member, where the cross-sectionis taken through a center of the catheter body and along a longitudinalaxis of the catheter body.

FIG. 5A is a conceptual cross-sectional view of a part of a catheterbody including a tapered structural support member, where thecross-section is taken through a center of the catheter body and along alongitudinal axis of the catheter body.

FIG. 5B is a conceptual cross-sectional view of the catheter body ofFIG. 5A taken along line A-A in FIG. 5A.

FIG. 5C is a conceptual cross-sectional view of the catheter body ofFIG. 5A taken along line B-B in FIG. 5A.

FIG. 6 is a flow diagram of an example method of forming the cathetersof FIGS. 1-5.

FIG. 7 is a flow diagram of an example method of forming the cathetersof FIGS. 1-5.

DETAILED DESCRIPTION

The disclosure describes a catheter that includes a relatively flexiblecatheter body with increased structural integrity that is configured tobe navigated through vasculature of a patient. Catheters may be used todiagnose and treat a variety of conditions, including thrombosis. Forexample, thrombosis occurs when a thrombus (e.g., a blood clot or otherembolus) forms and obstructs vasculature of a patient. In some medicalprocedures, to treat a patient with thrombosis, a clinician may positionan aspiration catheter in a blood vessel of the patient (i.e.,catheterization) near the thrombus, apply suction to the aspirationcatheter, and engage the thrombus with a tip of the aspiration catheter.This medical procedure may be, for example, A Direct Aspiration firstPass Technique (ADAPT) for acute stroke thrombectomy, or any otheraspiration of thrombus or other material from the neurovasculature orother blood vessels.

In addition to or instead of medical aspiration, a catheter can be usedto deliver a therapeutic device to a target treatment site withinvasculature (e.g., neurovasculature) of a patient to treat a defect inthe vasculature, such as, but not limited to, aneurysms or arteriovenousmalformations. The therapeutic neurovascular device may include anysuitable medical device configured to be used to treat a defect invasculature of a patient or used to facilitate treatment of theneurovasculature. For example, the therapeutic device can include athrombectomy device, a flow diverter, a stent, an aspiration catheter, adrug delivery catheter, a balloon catheter, a microvascular plug, afilter, an embolic retrieval device (e.g., a stent retriever or anaspiration catheter), or an implantable medical device, such as anembolic coil.

To position a catheter in a blood vessel of a patient, a clinician maypush a proximal portion (e.g., a proximal end) of the catheter toadvance the catheter through the blood vessel. Walls of the blood vesselmay guide a distal tip (e.g., at a distal end) of the catheter throughthe blood vessel. However, some blood vessels, such as cerebralarteries, have tortuous configurations. These tortuous configurationsmay include relatively low radius bends that sharply bend the catheteror create resistance along a longitudinal axis of the catheter. Asdiscussed in further detail below, the catheters described herein enablethe catheter to be navigated to a target site within vasculature of apatient with relatively high structural integrity e.g., by increasingadhesion between the structural support member and the outer jacketand/or inner liner and/or by supporting transitions in a segmented outerjacket using an increased density (e.g., pitch or braid density, whichcan be expressed in pics per inch) of the structural support member. Asa result, the catheters described herein may stabilize (e.g., resistdelamination between) the structural support member and the outer jacketand/or inner liner and/or resist buckling in the segmented outer jacket.

In some examples described herein, a catheter includes a structuralsupport member positioned between an inner liner and an outer jacket.Prior to or during assembly of the catheter, the structural supportmember can be surface treated by applying a surface treatment to theoverall surface or to at least a portion of the structural supportmember, such as an inner and/or outer radial surface. Some surfacetreatments can include physical treatments, such as roughening, toincrease a roughness and/or surface area of the structural supportmember in contact with the outer jacket, inner liner, and/or a supportlayer. Some surface treatments can include chemical treatments, such asfunctionalization or coatings, to increase a charge or generate reactivemoieties on the structural support member to bond with outer jacket,inner liner, and/or a support layer. The surface-treated structuralsupport member may more strongly and/or readily adhere to the outerjacket and/or inner liner, either directly or through an intermediatesupport layer, such that the structural support member may be lesslikely to separate from the outer jacket and/or inner liner in responseto compression or bending forces experienced while navigating thecatheter through the vasculature compared to catheters that do notinclude a surface treated structural support member.

In some examples, the surface treatment can be applied to, or in variousamount at, particular portions of the structural support member toincrease the adhesion between the particular portions of the structuralsupport member and the inner liner and/or outer jacket. Certain portionsof the structural support member may be more likely to experienceseparation from the inner liner and/or outer jacket than other portionsof the catheter, such as due to relatively higher forces or deformationexperienced at these portions or reduced inter-coil or inter-braidcontact between the inner liner and outer jacket at these portions. Forexample, during formation of the outer jacket, a higher density ordiameter section of the structural support member may reduce flow of anouter jacket material between structures (e.g., coils) of the structuralsupport member (e.g., during heat shrinking of the outer jacket materialor during a reflow process). This reduced flow may result in reducedcontact between the inner liner and the outer jacket, whether directly(as in a tri-layer catheter design) or via a support layer (as in aquad-layer catheter design). The structural support member may besurface treated to at least partly compensate for a smaller contact areabetween the inner liner and the outer jacket.

In examples described herein, a catheter includes an inner liner, anouter jacket that includes a plurality of outer jacket segments, and astructural support member positioned between at least a portion of theinner liner and the outer jacket. Each outer jacket segment islongitudinally adjacent to another outer jacket segment, and may havedifferent compositions or properties, such as different materials (e.g.,different chemical compositions), different durometers, and/or differentthicknesses. Due to structural discontinuities and/or differentcompositions or properties of the adjacent outer jacket segments, ajunction between adjacent outer jacket segments may be a relatively weakspot at which buckling or collapse of the catheter may be more likely tooccur. To reinforce the junction, the structural support member has avariable density that is relatively high (e.g., a higher coil pitch ormore pics per inch in the case of a braid) near the junction compared toa density at other portions of the structural support member. Forexample, an intermediate section of the structural support member thatis longitudinally aligned with a junction between two outer jacketsegments may have a relatively high density compared to adjacentsections of the structural support member proximal and distal to theintermediate section. The relatively high density section may resistcompression at the junction between the two outer jacket segments, suchthat the structural support member may be less likely to kink orcollapse at the junction in response to compression or bending forcesexperienced while navigating the catheter through the vasculaturecompared to catheters that do not include a relatively high densitysection of a structural support member at a junction between twoadjacent outer jacket segments.

In various ways described herein, example catheters may resist temporary(e.g., buckling) or permanent (e.g., delamination) deformation whenbeing navigated through vasculature having tortuous configurations. FIG.1 is a side elevation view of an example catheter 10, which includescatheter body 12 and hub 14. Catheter hub 14 is positioned at a proximalend of catheter 10 and defines an opening through which an inner lumen26 (shown in FIG. 2) of catheter body 12 may be accessed and, in someexamples, closed. For example, catheter hub 14 may include a luerconnector for connecting to another device, a hemostasis valve, oranother mechanism or combination of mechanisms. In some examples,catheter 10 includes strain relief member 11, which may be a part of hub14 or may be separate from hub 14. In other examples, the proximal endof catheter 10 can include another structure in addition or, or insteadof, hub 14.

Catheter body 12 is an elongated body that extends from proximal end 12Ato distal end 12B and defines at least one inner lumen 26 (e.g., oneinner lumen, two inner lumens, or three inner lumens) that terminates atdistal opening 13 defined by catheter body 12. In the example shown inFIG. 1, proximal end 12A of catheter body 12 is received within hub 14and is mechanically or otherwise connected to hub 14 via an adhesive,welding, or another suitable technique or combination of techniques.Opening 15 defined by hub 14 and located at proximal end 14A of hub 14is aligned with inner lumen 26 of catheter body 12, such that innerlumen 26 of catheter body 12 may be accessed via opening 15.

Catheter body 12 has a suitable length for accessing a target tissuesite within the patient from a vascular access point. The length may bemeasured along longitudinal axis 16 of catheter body 12. The targettissue site may depend on the medical procedure for which catheter 10 isused. For example, if catheter 10 is a distal access catheter used toaccess vasculature in a brain of a patient from a femoral artery accesspoint at the groin of the patient, catheter body 12 may have a length ofabout 129 centimeters (cm) to about 135 cm, such as about 132 cm,although other lengths may be used. In other examples, such as examplesin which catheter 10 is a distal access catheter used to accessvasculature in a brain of a patient from a radial artery access point,catheter body 12 may have a length of about 80 cm to about 120 cm, suchas about 85 cm, 90 cm, 95 cm, 100 cm, 105 cm, although other lengths maybe used (e.g., sheaths or radial intermediate catheters may be 5-8 cmlonger).

Catheter body 12 can be relatively thin-walled, such that it defines arelatively large inner diameter for a given outer diameter, which mayfurther contribute to the flexibility and kink-resistance of catheterbody 12. The wall thickness of catheter body 12 may be the differencebetween the outer diameter of catheter body 12 and the inner diameter ofcatheter body 12, as defined by inner lumen 26. For example, in someexamples, an outer diameter of catheter body 12 may be about 4 French toabout 12 French, such as about 5 French or about 6 French. Themeasurement term French, abbreviated Fr or F, is three times thediameter of a device as measured in mm. Thus, a 6 French diameter isabout 2 millimeters (mm), a 5 French diameter is about 1.67 mm, a 4French diameter is about 1.33 mm, and a 3 French diameter is about 1 mm.The term “about” or “approximately” as used herein with dimensions mayrefer to the exact numerical value or a range within the numerical valueresulting from manufacturing tolerances and/or within 1%, 5%, or 10% ofthe numerical value. For example, a length of about 10 mm refers to alength of 10 mm to the extent permitted by manufacturing tolerances, ora length of 10 mm+/−0.1 mm, +/−0.5 mm, or +/−1 mm in various examples.

In some examples, rather than being formed from two or more discrete andseparate longitudinally extending segments that are mechanicallyconnected to each other, e.g., at axial butt joints, catheter body 12may be substantially continuous along a length of catheter body 12. Forexample, catheter body 12 may include an inner liner that defines theinner lumen 26 of catheter body 12 and continuously extends fromproximal end 12A to distal end 12B of catheter body 12, and a structuralsupport member that extends across at least a part of the proximalportion 17A, at least part of the distal portion 17B, and the medialportion 17C of catheter body 12. A substantially continuous catheterbody 12 may be configured to better distribute forces in a longitudinaldirection (in a direction along longitudinal axis 16) and rotationaldirection (rotation about longitudinal axis 16) compared to a catheterbody including two or more longitudinally extending segments that aremechanically connected to each other. Thus, the substantially continuousconstruction of catheter body 12 may contribute to the ability of body12 to transfer axial pushing forces from a proximal portion 17A ofcatheter body 12 to a distal portion 17B, as well transfer rotationalforces (if any) applied from proximal portion 17A of catheter body 12 todistal portion 17B. While in some examples, as will be described withreference to FIGS. 3 and 4, catheter body 12 includes an outer jacketformed from two or more longitudinally extending segments that are in anabutting relationship, due to the continuous inner liner and thestructural support member that extends along a majority of the length ofcatheter body 12, catheter body 12 may still better distribute forcesand flexibility compared to a catheter body including two or morelongitudinal sections that are mechanically connected to each other.

In some examples, at least a portion of an outer surface of catheterbody 12 includes one or more coatings, such as, but not limited to, ananti-thrombogenic coating, which may help reduce the formation ofthrombi in vitro, an anti-microbial coating, and/or a lubricatingcoating. The lubricating coating may be configured to reduce staticfriction and/kinetic friction between catheter body 12 and tissue of thepatient as catheter body 12 is advanced through the vasculature. Thelubricating coating can be, for example, a hydrophilic coating. In someexamples, the entire working length of catheter body 12 (from distal end14B of hub 14 to distal end 12B) is coated with the hydrophilic coating.In other examples, only a portion of the working length of catheter body12 coated with the hydrophilic coating. This may provide a length ofcatheter body 12 distal to distal end 14B of hub 14 with which theclinician may grip catheter body 12, e.g., to rotate catheter body 12 orpush catheter body 12 through vasculature.

As described in further detail below, catheter body 12 may be used toaccess relatively distal locations in a patient, such as the MCA in abrain of a patient. The MCA, as well as other vasculature in the brainor other relatively distal tissue sites (e.g., relative to the vascularaccess point), may be relatively difficult to reach with a catheter, dueat least in part to the tortuous pathway (e.g., comprising relativelysharp twists and/or turns) through the vasculature to reach these tissuesites. Catheter body 12 may be structurally configured to be relativelyflexible, pushable, and kink-, buckle-, and delamination-resistant, sothat it may resist buckling when a pushing force is applied to arelatively proximal portion of catheter 10 to advance the catheter body12 distally through vasculature, resist kinking when traversing around atight turn in the vasculature, and/or so resist delamination and/orlayer separation when bending around a tight turn of the vasculature. Asone example, kinking or buckling may occur when a weak point of acatheter body, such as a transition between different structures ormaterials, undergoes deformation along (e.g., buckling) or away from(e.g., kinking) in response to a bending or compressive force. Asanother example, delamination may occur when two or more componentswithin a catheter body, such as an inner liner, an outer jacket, astructural support member, and/or a support layer between any of theinner liner, outer jacket, or structural support member, separate inresponse to a bending or compressive force. Kinking, buckling, and/ordelamination of catheter body 12 may hinder a clinician's efforts topush the catheter body distally, e.g., past a turn.

A characteristic that may contribute to at least the pushability,flexibility, and/or integrity of catheter body 12 is an adhesion betweenthe structural support member and either or both the outer jacket andthe inner liner. A surface of at least a portion of the structuralsupport member can be surface treated to increase an adhesion of thesurface to at least one of the inner liner or the outer jacket, such asdirectly or via a support layer. In some examples, the surface treatmentmay include physical treatments, such as roughening the surface of aportion of the structural support member to increase a surface roughnessof the surface; chemical treatments, such as chemically treating thesurface of a portion of the structural support member to increase acharge of the surface or to functionalize the surface with reactivemoieties; and coating treatments, such as coating the surface of aportion of the structural support member with a functional layer, suchas a reactive layer with reactive moieties. The surface-treated portionof the structural support member may more readily and/or strongly adhereto the inner liner, outer jacket, and/or support layer, therebyincreasing stability of the structural support member between the innerliner and the outer jacket and resisting separation due to compressionor bending. This increased adhesion may be particularly useful forportions of the structural support member that correspond to sections ofthe inner liner or outer jacket that may not be as firmly adhered. Forexample, a higher density section of a variable density structuralsupport member may have reduced surface contact between the inner linerand the outer jacket due to lower penetration of the outer jacketmaterial or an intermediate layer (e.g., a tie layer) between the coilsor braids of the structural support member.

Another characteristic that may contribute to at least the pushability,flexibility, and/or integrity of catheter body 12 is a variable densityof the structural support member in relation to the longitudinallyextending segments of the outer jacket. For example, the outer jacketmay include a plurality of outer jacket segments in which each outerjacket segment of the plurality is longitudinally adjacent to anotherouter jacket segment of the plurality. A junction between two outerjacket segments may be a relatively weak point that is more susceptibleto collapse in response to a longitudinal force, such as may beexperienced when a catheter is pushed. The structural support member mayhave an increased density near the junction to support and reinforce thejunction. For example, a first section of the structural support membermay have a relatively low density, a second section of the structuralsupport member distal to the first section may have a relatively highdensity, and a third section of the structural support member distal tothe second section may have a relatively low density. To reinforce thejunction between two outer jacket segments, the second, higher densitysection of the structural support member may be longitudinally alignedwith the junction. While the junction may have reduced resistance tocompression than the adjacent sections of the outer jacket, the higherdensity section of the structural support member may have increasedresistance to compression to reduce buckling and/or kinking at thejunction.

Another characteristic that may contribute to at least the pushability,flexibility, and/or integrity of catheter body 12 is a variable diameterof the structural support member and variable properties of the outerjacket. For example, a distal portion of the coiled structural supportmember may have a smaller diameter than a proximal portion of the coiledstructural support member. This smaller diameter distal section may haveincreased flexibility and may enable a thicker outer jacket having alower durometer, and therefore more flexible, material, while alsoenabling the catheter to maintain a relatively constant inner diameterof the inner liner and outer diameter of the outer jacket.

Any of the characteristics described herein that may contribute to atleast the pushability, flexibility, and/or integrity of catheter body 12may be used alone or in combination with each other.

FIG. 2 is a conceptual cross-sectional view of a part of catheter body12 including distal end 12B, where the cross-section is taken through acenter of catheter body 12 along longitudinal axis 16. As illustrated inthe quad-layer configuration of FIG. 2, catheter body 12 includes innerliner 18, structural support member 20, support layer 22, and outerjacket 24; however, in other examples, catheter body 12 may not includesupport layer 22, such as in a tri-layer configuration as illustrated inFIGS. 3 and 4.

Inner liner 18 defines inner lumen 26 of catheter body 12, inner lumen26 extending from proximal end 12A to distal end 12B and defining apassageway extending from proximal end 12A to distal opening 13 atdistal end 12B of catheter body 12. Inner lumen 26 may be sized toreceive a medical device (e.g., another catheter, a guidewire, anembolic protection device, a stent, or any combination thereof), atherapeutic agent, or the like. At least the inner surface of innerliner 18 defining inner lumen 26 may be lubricious in some examples inorder to facilitate the introduction and passage of a device, atherapeutic agent, or the like, through inner lumen 26. For example, thematerial from which the entire inner liner 18 is formed may belubricious, or inner liner 18 may be formed from two or more materials,where the material that defines inner lumen 26 may be more lubriciousthan the material that interfaces with structural support member 20 andsupport layer 22. In addition to, or instead of, being formed from alubricious material, in some examples, an inner surface of inner liner18 is coated with a lubricious coating. Example materials from whichinner liner 18 may be formed include, but are not limited to,polytetrafluoroethylene (PTFE), fluoropolymer, perfluoroalkyoxy alkane(PFA), fluorinated ethylene propylene (FEP), or any combination thereof.For example, inner liner 18 may be formed from an etched PTFE, e.g., mayconsist essentially of an etched PTFE.

Outer jacket 24 is positioned radially outward of inner liner 18 andstructural support member 20, and, in some examples, defines an outersurface of catheter body 12. Although a coating or another material maybe applied over the outer surface of outer jacket 24, outer jacket 24may substantially define a shape and size of the outer surface ofcatheter body 12. Outer jacket 24, together with structural supportmember 20 and inner liner 18, may be configured to define catheter body12 having the desired flexibility, kink resistance, and pushabilitycharacteristics. Outer jacket 24 may have stiffness characteristics thatcontribute to the desired stiffness profile of catheter body 12. Forexample, outer jacket 24 may be formed to have a stiffness thatdecreases from a proximal portion 17A of catheter body 12 to a distalportion 17B. In some examples, outer jacket 24 may be formed from two ormore different materials that enable outer jacket 24 to exhibit thedesired stiffness characteristics, such as may described further inFIGS. 3 and 4 below.

Structural support member 20 is configured to increase the structuralintegrity of catheter body 12 while allowing catheter body 12 to remainrelatively flexible. For example, structural support member 20 may beconfigured to help catheter body 12 substantially maintain itscross-sectional shape or at least help prevent catheter body 12 frombuckling or kinking as it is navigated through tortuous anatomy.Structural support member 20, together with inner liner 18, outer jacket24, and optionally support layer 22, may help distribute both pushingand rotational forces along a length of catheter body 12, which may helpprevent kinking of body 12 upon rotation of body 12 or help preventbuckling of body 12 upon application of a pushing force to body 12. As aresult, a clinician may apply pushing forces, rotational forces, orboth, to proximal portion 17A of catheter body 12, and such forces maycause distal portion 17B of catheter body 12 to advance distally,rotate, or both, respectively. In the example shown in FIG. 2,structural support member 20 extends along only a portion of a length ofcatheter body 12; however, in other examples, structural support member20 may extend along an entire length of catheter body 12.

In some examples, structural support member 20 includes a generallytubular braided structure (e.g., as illustrated by portion 40 ofcatheter body 12 in FIG. 4), a coil member defining a plurality of turns(e.g., as illustrated by portion 30 of catheter body 12 in FIG. 3), or acombination of a braided structure and a coil member. Thus, althoughexamples of the disclosure may describe structural support member 20 asa coil, in some other examples, the catheter bodies described herein mayinclude a braided structure instead of a coil or a braided structure inaddition to a coil. For example, a proximal portion of structuralsupport member 20 may include a braided structure and a distal portionof structural support member 20 may include a coil member, or viceversa. Structural support member 20 can be made from any suitablematerial, such as, but not limited to, a metal (e.g., a nickel titaniumalloy, stainless steel, tungsten, titanium, gold, platinum, palladium,tantalum, silver, or a nickel-chromium alloy, a cobalt-chromium alloy,or the like), a polymer, a fiber, or any combination thereof. In someexamples, structural support member 20 may include one or more metalwires braided or coiled around inner liner 18. The metal wires mayinclude round wires, flat-round wires, flat wires, or any combinationthereof.

Structural support member 20 may be coupled, adhered, and/ormechanically connected to at least a portion of an outer surface ofinner liner 18 and/or at least a portion of an inner surface of outerjacket 24. In some examples, structural support member 20 may bedirectly coupled, adhered, and/or mechanically connected to at least aportion of an outer surface of inner liner 18 and/or at least a portionof an inner surface of outer jacket 24. For example, while catheter 10of FIG. 2 illustrates a quad-layer configuration that includes supportlayer 22, in some examples, such as illustrated in portion 30 of FIG. 3or portion 40 of FIG. 4, catheter 10 may include a tri-layerconfiguration that does not include support layer 22. In such examples,the inner surface of outer jacket 24 and the outer surface of innerliner 18 may, at least partly, directly contact and/or adhere to eachother between braids or coils of structural support member 20.

In other examples, such as illustrated in FIG. 2, structural supportmember 20 may be indirectly coupled, adhered, and/or mechanicallyconnected to at least a portion of the outer surface of inner liner 18and/or at least a portion of the inner surface of outer jacket 24 viasupport layer 22. For example, support layer 22 may be a thermoplasticmaterial or a thermoset material, such as a thermoset polymer and/or athermoset adhesive. In some examples, support layer 22 is positionedbetween the entire length of structural support member 20 and innerliner 18, while in other examples, support layer 22 is only positionedbetween a part of the length of structural support member 20 and innerliner 18.

In example catheters that do not include support layer 22, such asillustrated in FIGS. 3 and 4, outer jacket 24 may be configured to fillat least part of the spaces (e.g., part or all of the spaces) betweenportions of structural support member 20, e.g., the spaces between turnsof structural support member 20 in examples in which member 20 is a coilmember or the spaces defined between pics of a braid. In examplecatheters that include support layer 22, support layer 22 may beconfigured to fill at least part of the spaces between portions ofstructural support member 20.

In some instances, the presence of outer jacket 24 and/or support layer22 between turns of member 20 may help adhere outer jacket 24 and innerliner 18 to each other and securely integrate structural support member20 into catheter body 12, such that structural support member 20 mayresist detachment during bending or compression of catheter 10. Forexample, at least by minimizing or even eliminating voids between turnsof structural support member 20, such as may be caused by insufficientflow of a material of outer jacket 24, outer jacket 24 and/or supportlayer 22 may provide a higher contact surface between inner liner 18 andouter jacket 24, which may better distribute pushing or torqueing forcesapplied to proximal portion 17A of catheter body 12 to distal portion17B. In addition or instead, minimizing or even eliminating voidsbetween turns of structural support member 20 may provide longitudinalsupport to structural support member 20 to secure structural supportmember within catheter body 12.

In some instances, the presence of outer jacket 24 and/or support layer22 between turns of member 20 may help distribute the flexibilityprovided by member 20 along the length of member 20, which may helpprevent catheter body 12 from kinking. For example, at least byeliminating voids between turns of structural support member 20, outerjacket 24 and/or support layer 22 may transfer the flexing motion fromstructural support member 20 along a length of catheter body 12. In someexamples, support layer 22 has a thickness (measured in a directionorthogonal to longitudinal axis 16) that is greater than or equal to across-sectional dimension of the wire that forms the member 20, suchthat layer 22 is at least partially positioned between outer jacket 24and structural support member 20. In other examples, support layer 22has a thickness that is less than or equal to a cross-sectionaldimension of the wire that forms the structural support member 20, suchthat support layer 22 is not positioned between outer jacket 24 andstructural support member 20.

In some examples, to increase adhesion of structural support member 20to inner liner 18 and/or outer jacket 24, a surface of at least aportion of structural support member 20 is surface treated. A surface ofstructural support member 20 that has been surface treated may includeenhanced surface properties, such as roughness, charge, or reactivemoieties. These surfaces of structural support member 20 may morestrongly or readily adhere to inner liner 18, support layer 22, and/orouter jacket 24 compared to surface properties of a similar, butuntreated, structural support member. As a result, structural supportmember 20 may be better integrated into catheter body 12 and less likelyto displace in response to compressive or bending forces on catheter 10.

Increased adhesion of structural support member 20 to inner liner 18,outer jacket 24, and/or support layer 22 may be measured and/orquantified in one or more of a variety of ways including, but notlimited to, shear strength (e.g., structural support member 20 detachingfrom inner liner 18 and/or outer jacket 24 along longitudinal axis 16),peel strength (e.g., structural support member 20 detaching from innerliner 18 and/or outer jacket 24 radially from longitudinal axis 16), andthe like. In some examples, structural support member 20 and inner liner18 and/or outer jacket 24 may have increased shear strength compared toa structural support member that does not include a surface treatment.In some examples, a shear strength of structural support member 20 maybe greater than or equal to about twice a shear strength of a similarstructural support member that does not include the surface treatment.

In some examples, the surface treatment may include a physicaltreatment. A physical treatment includes any treatment that results inan increase in contact area of the surface of structural support member20 for bonding with inner layer 18, outer jacket 24, and/or supportlayer 22, or an increase in mechanical interlocking between the surfaceof structural support member 20 and inner liner 18, outer jacket 24,and/or support layer 22. For example, a physical treatment may increasea surface area or surface deviation (e.g., slope angle) of the surfaceof structural support member 20. Example physical treatments that may beused include, but are not limited to, mechanical roughening, laserroughening, abrasion, or the like, and combinations thereof.

In some examples, the surface treatment may include roughening thesurface of a portion of structural support member 20, such that theportion of structural support member 20 may have an increased surfaceroughness of the surface. An increased surface roughness may be, forexample, an increased contact area, contact slope, and/or fractality ofthe surface of structural support member 20 with inner liner 18, outerjacket 24, and/or support layer 22, thereby increasing adhesion betweenstructural support member 20 and inner liner 18, outer jacket 24, and/orsupport layer 22. In some examples, the surface of at least a portion ofthe structural support member 20 includes a surface roughness greaterthan about 2 microns Ra (arithmetical mean deviation of profile) and/orabout 100 microns Rz (maximum height of profile).

In some examples, the surface treatment may include a chemicaltreatment. A chemical treatment includes any treatment that results inan increase in chemical bonding between structural support member 20 andinner liner 18, outer jacket 24, and/or support layer 22. For example, achemical treatment may increase a charge or reactivity of the surface ofstructural support member 20 to increase intermolecular forces (e.g.,Van Der Waals forces, hydrogen bonding, ionic bonding, and/or covalentbonding) between structural support member 20 and inner liner 18, outerjacket 24, and/or support layer 22. One or more of a variety of chemicaltreatments may be used including, but not limited to, alkalinetreatment, acid treatment, ionization, protonation, deprotonation,electric field charge, or the like, and combinations thereof.

In some examples, the surface treatment may include chemically treatingthe surface of a portion of structural support member 20, such that theportion of structural support member 20 may have an increased charge atthe surface. An increased charge of the surface may be opposite to acharge of inner liner 18, outer jacket 24, and/or support layer 22,thereby increasing an electrostatic attraction between structuralsupport member 20 and inner liner 18, outer jacket 24, and/or supportlayer 22. For example, structural support member 20 may include apositive charge, while outer jacket 24 may include a negative charge,such that structural support member 20 and outer jacket 24 may beelectrostatically attracted to each other.

In some examples, the surface treatment may include chemically treatingthe surface of a portion of structural support member 20, such that theportion of structural support member may be functionalized with reactivemoieties. For example, the surface of structural support member 20 maybe reacted with an acid or base to create reactive moieties, such asamines, carboxylic acids, or other reactive groups configured to reactwith polymers. Inner liner 18, outer jacket 24, and/or support layer 22may include polymers that include various functional groups capable ofreacting with the reactive moieties on structural support member 20.Reactive moieties on the structural support layer may bond (e.g.,covalently) with the functional groups of inner liner 18, outer jacket24, and/or support layer 22. As a result, the surface of at least theportion of structural support member 20 may be covalently bonded to atleast one of inner liner 18 or outer jacket 24.

In some examples, the surface treatment may include coating treatments,such as coating the surface of a portion of structural support member 20with a functional layer, such as a reactive layer with reactivemoieties. Rather than provide surface properties through a directsurface treatment of structural support member 20, a functional layermay provide the roughness, charge, and/or reactive properties describedabove with respect to the physical or chemical treatments. For example,the surface of the structural support member 20 may include a polymercoating that includes reactive moieties configured to react withfunctional groups of inner liner 18, outer jacket 24, and/or supportlayer 22. As a result, the surface of at least the portion of structuralsupport member 20 may include a coating covalently bonded to at leastone of inner liner 18 or outer jacket 24.

In some instances, structural support member 20 may be surface treatedfor contact with only one of inner liner 18 or outer jacket 24. As oneexample, structural support member 20 may be selectively surface treatedon an inner radial surface of structural support member 20 without beingsurface treated on an outer radial surface of structural support member20, such that structural support member 20 may have increased adhesionto inner liner 18 or support layer 22 between inner liner 18 andstructural support member 20. During positioning of structural supportmember 20 on inner liner 18, the increased adhesion may reduce movementof structural support member 20. As another example, structural supportmember 20 may be surface treated on an outer radial surface ofstructural support member 20 without being surface treated on an innerradial surface of structural support member 20, such that structuralsupport member 20 may have increased adhesion to outer jacket 24 orsupport layer 22 between outer jacket 24 and structural support member20. During formation of outer jacket 24, the surface treatment mayincrease a surface area and/or reactivity of the surface of structuralsupport member 20, such that a material of outer jacket 24 may morestrongly bond with the surface of structural support member 20. In otherinstances, structural support member 20 may be surface treated forcontact with both inner liner 18 and outer jacket 24

In some examples, the surface treatment can be applied to, or present invarious amounts at, one or more particular portions of structuralsupport member 20 to increase the adhesion between structural supportmember 20 and inner liner 18 and/or outer jacket 24. For example, theseone or more portions that are surface treated can be certain portions ofstructural support member 20 that may be more likely to experiencestresses that can cause separation from inner liner 18 and/or outerjacket 24 than other portions of structural support member 20. Forexample, a surface of a first portion of structural support member 20,such as a more distal portion, may be surface treated and a surface of asecond portion of structural support member 20, such as a more proximalportion, may not surface treated. As a result, the surface of the firstportion of structural support member 20 may have different surfaceproperties than the surface of the second portion of structural supportmember 20. For example, the surface of the first portion of structuralsupport member 20 may have a first surface roughness and a surface ofthe second portion of structural support member 20 may have a secondsurface roughness that is less than the first surface roughness. In someexamples, a shear strength of the first portion is greater than at leastabout 20% higher than a shear strength of the second portion.

In some examples, one or more portions of structural support member 20that may be subject to relatively high deformation may be surfacetreated. For example, a first portion of structural support member 20near distal opening 13 may be adjacent to a relatively low durometersection of outer jacket 24 that is more compressible. During navigationof catheter 10 through vasculature, the first portion may experience arelatively high amount of deformation that may cause delamination ordetachment of outer jacket 24 from structural support member 20.

In some examples, surfaces of one or more portions of structural supportmember 20 having a relatively high density (e.g., coil pitch or pics perinch) may be surface treated. For example, a first portion of structuralsupport member 20 may have a relatively high coil pitch and a secondportion of structural support member 20 may have a relatively low coilpitch. Due to the higher density, inner liner 18 and outer jacket 24 mayhave lower inter-coil or inter-braid contact in the first portion thanthe second portion of structural support member 20. For example, duringformation of outer jacket 24, the first portion of structural supportmember 20 may have reduced flow of an outer jacket material betweenstructures (e.g., adjacent turns of a coil) of structural support member20. This reduced flow of the outer jacket material may result in reducedcontact area between inner liner 18 and outer jacket 24 in the firstsection compared to the second section, whether directly (as in atri-layer catheter configuration) or via support layer 22 (as in aquad-layer catheter configuration illustrated in FIG. 2).

In some examples, surfaces of one or more portions of structural supportmember 20 having a relatively larger diameter may be surface treated.For example, a first portion of structural support member 20 may have arelatively small diameter and a second portion of structural supportmember 20 may have a relatively large diameter. Due to the largerdiameter in the second portion of structural support member 20, innerliner 18 and outer jacket 24 may have lower inter-coil or inter-braidcontact area in the second portion than the first portion of structuralsupport member 20.

In the example illustrated in FIG. 2, structural support member 20 isformed from a wire, such as a rounded (in cross-section) wire, that isshaped to define a coil. In other examples, member 20 may be formed, atleast in part, from a flat (in cross-section) wire that is shaped todefine a coil. A rounded wire may define a coil member having a lowersurface area than a flat wire, such that, for a given length ofstructural support member 20, inner liner 18 and/or outer jacket 24 mayhave a higher contact area between coils of structural support member20. A flat wire may define a coil member having a higher surface areathan a round wire, such that, for a given length of structural supportmember 20, structural support member 20 may have a higher contact areawith inner liner 18 and/or outer jacket 24.

The wire from which member 20 is formed can be a metal wire. In someexamples, the wire is formed from a shape memory material, such a nickeltitanium alloy (Nitinol). In other examples, the wire is formed fromstainless steel. In some cases, a nickel titanium alloy may be morecrush resistant than stainless steel, and, therefore, may be used toform a structural support member 20 of a catheter that is more resistantto kinking and buckling compared to stainless steel. In addition, asdescribed in further detail below, a shape memory material may allowstructural support member 20 to be formed before it is positioned overinner liner 18. For example, the pitch and diameter of member 20 may bedefined before member 20 is positioned over inner liner 18, which mayprovide certain advantages (discussed below). In contrast, when member20 is formed from stainless steel, the pitch and diameter of member 20may be defined as member 20 is wound over inner liner 18.

In some examples, structural support member 20 includes multiple,longitudinally adjacent structures (e.g., connected to each other,abutting but not connected to each other, or with a gap therebetween).In other examples, structural support member 20 is formed from a singlewire that defines a coil member that changes in outer diameter and innerdiameter of structural support member 20, changes in outer diameter ofthe coil member, and changes in pitch along the length of member 20. Thesingle wire may be seamless (or joint-less) in that there are no joints(e.g., butt joints) between separate portions of wire that are connectedtogether to define a longer wire; rather, the wire has a unitary bodyconstruction. In some examples, a contemporaneous change in pitch andinner and outer diameters of the structural support member 20 includinga single, seamless wire may be made possible, at least in part, by ashape memory material from which the wire is formed. Defining member 20from a single, seamless wire may increase the structural integrity ofcatheter body 12 compared to examples in which member 20 is formed frommultiple wires that are joined together. For example, the joints betweenwires may adversely affect the tensile strength or lateral flexibilityof member 20, which may adversely affect the flexibility and pushabilityof catheter body 12.

In examples in which structural support member 20 includes a coil (e.g.,a helical coil), the flexibility of structural support member 20 may be,at least in part, a function of a pitch of the coil. For a given wire, alarger pitch results in larger gaps between adjacent turns of the wireforming member 20 and a higher degree of flexibility. The pitch can be,for example, the width of one complete turn of wire, measured in adirection along longitudinal axis 16. In some examples, a pitch ofstructural support member 20 varies along a length of structural supportmember 20, such that a stiffness (or flexibility) varies along thelength. The pitch may continuously vary along the length of member 20,or may progressively change, e.g., include different sections, eachsection having a respective pitch.

The flexibility of outer jacket 24 may be, at least in part, a functionof a composition, a hardness (e.g., durometer), and/or a thickness ofouter jacket 24. For example, a higher durometer may result in lesscompressibility and a lower degree of flexibility. To configure catheterbody 12 with a particular flexibility profile (e.g., a flexibility alonglongitudinal axis 16), outer jacket 24 may include multiple outer jacketsegments that include varied properties and are supported by a variabledensity structural support member 20. FIGS. 3-4 illustrate variouscatheters that include variable density structural support members 20for supporting one or more junctions between segments of outer jacket24.

FIG. 3 is a conceptual cross-sectional view of a portion 30 of anexample catheter body (e.g., catheter body 12 of FIG. 2) including acoiled structural support member 20, where the cross-section is takenthrough a center of the catheter body and along the longitudinal axis(e.g., longitudinal axis 16 in FIG. 1) of the catheter body. Whilecatheter body 12 is primarily referred to in the description of FIGS. 3and 4, in other examples, portion 30 can be a portion of anothercatheter body.

In the example shown in FIG. 3, portion 30 of catheter body 12 includesinner liner 18, outer jacket 24, and structural support member 20. Outerjacket 24 includes a plurality of outer jacket segments 34A and 34B(collectively referred to herein as “segments 34” or generally referredto individually as “segment 34”). In the example of FIG. 3, only a firstouter jacket segment 34A and a second outer jacket segment 34B areillustrated; however, catheter body 12 can include any number of outerjacket segments 34. Segments 34 can each be, for example, sleeves (e.g.,tubular sleeves) that are configured to be positioned over inner liner18 and structural support member 20, and, if present, support layer 22,as will be described further in FIGS. 5A-5C.

Segments 34 are situated longitudinally adjacent to each other, e.g., inan abutting relationship, and, in some examples, can be mechanicallyconnected together to define outer jacket 24 using any suitabletechnique, such as by welding, an adhesive, heating/reflow, or anycombination thereof. Adjacent outer jacket segments 34 form a junction32 between the adjacent outer jacket segments 34; as illustrated in FIG.3, outer jacket segment 34A forms junction 32 with outer jacket segment34B. Segments 34 may each have any suitable length, which may beselected based on the desired flexibility profile of catheter body 12.In some examples, proximal, distal, and intermediate portions 17A-17C(FIG. 1) of catheter body 12 may have their own respective outer jacketsegments 34 that each begin and end at the proximal and distal ends ofthe corresponding catheter body portions 17A-17C. In other examples, oneof outer jacket segments 34 may extend at least over both proximalportion 17A and intermediate portion 17C, and/or over both intermediateportion 17C and distal portion 17B.

The stiffness and/or hardness (e.g., durometer) of outer jacket 24contribute to the flexibility and structural integrity of catheter body12. Accordingly, the composition and properties of each of segments 34,such as durometer and/or thickness, may be selected to assist inproviding portion 30 of catheter body 12 with the desired flexibilitycharacteristics.

In some examples, the composition of each of segments 34 may be selectedto provide catheter body 12 with the desired flexibilitycharacteristics. For example, different materials may have differentproperties, such as durometer, compressibility, elasticity, and thelike. In some examples, at least two outer jacket segments 34 are formedfrom different materials (e.g., materials having different chemicalcompositions and/or different material characteristics). Examplematerials for segments 34 include, but are not limited to, polymers,such as a polyether block amide (e.g., PEBAX®, commercially availablefrom Arkema Group of Colombes, France), an aliphatic polyamide (e.g.,Grilamid®, commercially available from EMS-Chemie of Sumter, S.C.),another thermoplastic elastomer or other thermoplastic material, orcombinations thereof. In one example, a more proximal segment, such assegment 34A, is formed from an aliphatic polyamide and a more distalsegment, such as segment 34B, is formed from a polyether block amide.The compositions of the polyether block amide may be modified to achievesegments 34 having different durometers.

In some examples, the durometers of each of segments 34 may be selectedto help provide catheter body 12 with the desired flexibilitycharacteristics. For example, at least two outer jacket segments 34 mayhave different durometers. In some examples, segments 34 may have adurometer between about 30 A-100 A or 25D and about 90D. In otherexamples, however, one or more of the segments 34 may have otherhardness values. The hardness of the segments 34 may be selected toobtain more or less flexibility, torqueability, and pushability for allor part of catheter body 12.

In some examples, such as example portions of catheter body 12 in whichcatheter body 12 increases in flexibility from proximal end 12A towardsdistal end 12B, the durometer of two adjacent outer jacket segments 34may decrease in a direction from a proximal end of outer jacket 24towards a distal end. For example, a durometer of first outer jacketsegment 34A may be greater than a durometer of second outer jacketsegment 34B. As a result, catheter body 12 may be more flexible fornavigating catheter 10 through vasculature of a patient.

In some examples, such as example portions of catheter body 12 in whichcatheter body 12 decreases in flexibility along any part of catheterbody 12 between from proximal end 12A towards distal end 12B, thedurometer of two adjacent outer jacket segments 34 may increase in adirection from a proximal end of outer jacket 24 towards a distal end.For example, a durometer of first outer jacket segment 34A may be lessthan a durometer of second outer jacket segment 34B. While it may bedesirable in some cases to provide a catheter body 12 having arelatively flexible distal portion, as explained above, increasing thedurometer of a distal-most section of outer jacket 24 relative to a moreproximal section that is directly adjacent to the distal-most section,may provide certain advantages. For example, increasing the durometer ofthe distal-most section may configure distal opening 13 of catheter body12 to resist geometric deformation when distal opening 13 (FIG. 1) ofcatheter body 12 is engaged with a guidewire, which may help support thenavigation of catheter body 12 through vasculature. The distal-mostsection of outer jacket 24 that exhibits the increased stiffness may bea relatively small length of catheter body 12 and, therefore, may notaffect the overall flexibility of catheter body 12.

In some examples, structural support member 20 includes one or moresections that includes different properties related to a flexibility ofcatheter body 12, such as density of structures of structural supportmember 20 and diameter of structural support member 20. In the exampleof FIG. 3, structural support member 20 includes a first section 36A, asecond section 36B distal to first section 36A, and a third section 36Cdistal to second section 36B (referred to collectively as “sections 36”and individually generically as “section 36”).

In some examples, structural support member 20 includes one or morerelatively high density sections 36 interspersed with relatively lowdensity sections 36. Due to discontinuities between and/or differentproperties of the adjacent outer jacket segments 34, junction 32 betweenadjacent outer jacket segments 34 may be a relatively weak spot at whichcatheter body 12 may be more likely to buckle, kink, or collapse. Asexplained above, a density of structural support member 20 may beinversely proportional to a compressibility of structural support member20, such that the relatively high density sections of structural supportmember 20 may lower flexibility and/or higher compressibility than therelatively low density sections of structural support member 20. In someexamples, to reinforce junction 32, structural support member 20 has avariable density that is higher near junction 32. For example, in theexample of FIG. 3, first section 36A of structural support member 20 hasa first density, second section 36B of structural support member 20 hasa second density, and third section 36C of structural support member 20has a third density, where the second density of second section 36B ishigher than the first and third densities of first section 36A and thirdsection 36C, respectively.

In some examples, structural support member 20 includes a coilcomprising different sections having different, respective pitches. Anincreasing density of structural support member 20 may correspond to adecreasing pitch (e.g., spacing between coils or braids) of structuralsupport member 20. As shown in FIG. 3, a pitch of structural supportmember 20 decreases in a distal direction from first section 36A tosecond section 36B and increases in the distal direction from secondsection 36B to third section 36C. In one example, a pitch of a higherdensity section of structural support member 20, such as second section36B, may be greater than about 25% and less than about 75% of a pitch ofan adjacent lower density portion 36 of structural support member 20,such as first section 36A or third section 36C. While sections 36 areillustrated as having transition in density that are step-wise, in someexamples, transitions in density of structural support member 20 may begradual. In some examples, a pitch of structural support member may bebetween about 0.00225 inches (about 0.057 mm) to about 0.0070 inches(about 0.018 mm).

Second section 36B is longitudinally aligned with junction 32 betweenfirst outer jacket segment 34A and second outer jacket segment 34B. Forexample, second section 36B may longitudinally overlap a portion offirst outer jacket segment 34A and second outer jacket segment 34B, suchas greater than about 5 mm (measured along longitudinal axis 16). Therelatively high density of second section 36B may enable portion 30 ofcatheter body 12 to resist compression, and therefore buckling, atjunction 32, such that structural support member 20 may be less likelyto collapse at junction 32 in response to compression or bending forcesexperienced while navigating catheter 10 through the vasculature of apatient compared to catheters that do not include a relatively highdensity section of a structural support member at a junction between twoadjacent outer jacket segments.

In some examples, a surface of one or more sections of structuralsupport member 20 may be surface treated to increase an adhesion of thesurface to at least one of inner liner 18 and/or outer jacket 24. Forexample, as explained with respect to FIG. 2 above, a portion ofstructural support member 20 having a relatively high density mayexhibit a reduced flow of outer jacket material between structures ofstructural support member 20 and/or reduced contact area with innerliner 18 and/or support layer 22. The surface treatment may helpcompensate for any adverse impacts to the kink, compression, or bucklingof catheter body 12 resistance attributable to this reduced contactarea. In the example of FIG. 3, second section 36B includes a higherdensity, such that at least second section 36B of structural supportmember 20 may be surface treated to increase an adhesion of the surfaceof second section 36B to at least one of inner liner 18 and/or firstouter jacket segment 34A and/or second outer jacket segment 34B.

During navigation of catheter 10 through vasculature of a patient,bending of catheter body 12 may exert compressive forces on an insideradius of catheter body 12, such as at portion 30. Without variabledensity structural support member 20, the compressive forces may causeportion 30 to kink or buckle near junction 32. However, the higherdensity of second section 36B of structural support member 20 mayreinforce junction 32 to more evenly distribute forces, such as toportions of catheter body 12 that are adjacent to junction 32.

In some instances, a variable density structural support member, incombination with a variable composition, durometer, and/or thicknessouter jacket 24, may further configure a flexibility of a catheter body.FIG. 4 is a conceptual cross-sectional view of a portion 40 of acatheter body (e.g., catheter body 12 of FIG. 2) including a braidedstructural support member 21, where the cross-section is taken through acenter of catheter body 12 and along a longitudinal axis of catheterbody 12. Braided structural support member 21 may be an example ofstructural support member 20 of FIG. 2, such that features of braidedstructural support member 21 may apply to structural support member 20of FIG. 2, and vice versa.

Portion 40 of catheter body 12 includes inner liner 18, outer jacket 24,and structural support member 21. Outer jacket 24 includes a pluralityof outer jacket segments 44A, 44B, and 44C (collectively referred toherein as “segments 44” or generally referred to individually as“segment 44”). In the example of FIG. 4, only a first outer jacketsegment 44A, a second outer jacket segment 44B, and a third outer jacketsegment 44C are illustrated; however, portion 40 and catheter body 12can include any suitable number of outer jacket segments 44 in otherexamples. Adjacent outer jacket segments 44 form a junction 42 betweenthe adjacent outer jacket segments 44; as illustrated in FIG. 4, outerjacket segment 44A forms junction 42A with outer jacket segment 44B andouter jacket segment 44B forms junction 42B with outer jacket segment44C. Segments 44 may be similar to segments 34 of FIG. 3 describedabove.

In some examples, structural support member 21 includes one or moresections that include different properties related to a flexibility ofcatheter body 12, such as density of structures of structural supportmember 21 and diameter of structural support member 21. In the exampleof FIG. 4, structural support member 21 includes a first section 46A, asecond section 46B distal to first section 46A, and a third section 46Cdistal to second section 46B (referred to collectively as “sections 46”and individually generically as “section 46”). Sections 46 may besimilar to sections 36 of FIG. 3 described above.

In some examples, structural support member 21 may be configured toreinforce one or more junctions 42 and one or more outer jacket segments44. For example, the flexibility of catheter body 12 may be, at least inpart, a function of the flexibility of structural support member 21 andouter jacket 24. As such, the various flexibility properties ofdifferent structural support member sections 46 and outer jacketsegments 44 may be configured to, in combination, produce a desiredflexibility profile of portion 40 of catheter body 12.

As one example, in the example of FIG. 4, first section 46A ofstructural support member 21 is adjacent (e.g., in a radial direction)to first outer jacket segment 44A, second section 46B of structuralsupport member 21 is adjacent to second outer jacket segment 44B, andthird section 46C of structural support member 21 is adjacent to thirdouter jacket segment 44C. Outer jacket 24 may exhibit a graduallydecreasing durometer, such that first outer jacket segment 44A has afirst durometer, second outer jacket segment 44B has a second durometerthat is lower than the first durometer of first outer jacket segment44A, and third outer jacket segment 44C has a third durometer that islower than the first and second durometers of first outer jacket segment44A and second outer jacket segment 44B, respectively. First section 46Aof structural support member 21 has a first density, second section 46Bof structural support member 21 has a second density, and third section46C of structural support member 21 has a third density, such that thesecond density of second section 46B is higher than the first and thirddensities of first section 46A and third section 46C, respectively. As aresult, portion 40 forms a generally three-part catheter body 12 thatincludes a proximal portion having a relatively low density andrelatively high durometer for a relatively low net flexibility, anintermediate portion having a relatively high density and relativelymoderate durometer for a relatively moderate net flexibility, and adistal portion having a relatively low density and relatively lowdurometer for a relatively high net flexibility. As shown in FIG. 4,second section 46B overlaps a portion of each of first outer jacketsegment 44A and third outer jacket segment 44C to reinforce junctions42A and 42B. In this way, catheter bodies incorporating variableflexibility features in structural support member 21 and outer jacket 24may configure more specific flexibility profiles with increasedstructural integrity.

In some examples, catheters described herein may include a structuralsupport member that may change in diameter along a length of thestructural support member. FIG. 5A is a conceptual cross-sectional viewof a part of a catheter body including a tapered structural supportmember, where the cross-section is taken through a center of thecatheter body and along a longitudinal axis of the catheter body.Portion 50 of catheter body 12 includes inner liner 18, outer jacket 24,structural support member 20, and support layer 22. However, in otherexamples, such as catheter bodies or portions of catheter bodies thatinclude a tri-layer configuration, support layer 22 may not be included.Portion 50 includes a proximal portion 52A and a distal portion 52B.

FIG. 5B is a conceptual cross-sectional view of proximal portion 52A ofportion 50 of catheter body 12 of FIG. 5A taken along line A-A in FIG.5A, while FIG. 5C is a conceptual cross-sectional view of distal portion52B of portion 50 of catheter body 12 of FIG. 5A taken along line B-B inFIG. 5A. In the examples of FIG. 5A-5C, outer jacket 24 includes aproximal outer jacket segment 60A and a distal outer jacket segment 60B(collectively referred to as “segments 60” and individually referred toas “segment 60”); support layer 22 includes a proximal section 58A and adistal section 58B (collectively referred to as “segments 58” andindividually referred to as “segment 58”); and structural support member20 includes a proximal section 56A and a distal section 56B(collectively referred to as “section 56” and individually referred toas “section 56”).

In some examples, structural support member 20 may taper and/or expandat various portions, such as portion 50, of catheter body 12. Asillustrated in the example portion 50 of FIGS. 5A-5C, structural supportmember 20 tapers from a first diameter at proximal portion 52A to asecond diameter at distal portion 52B. For example, structural supportmember 20 may taper from a first, larger coil diameter to a second,smaller coil diameter. The diameter can be measured, for example, aninner diameter of structural support member 20 and/or an outer diameterof structural support member 20. In the example shown in FIGS. 5A-5C,proximal section 56A of structural support member 20 has a first coilouter diameter and distal section 56B of structural support member 20has a second coil outer diameter that is smaller than the first coilouter diameter, such that structural support member 20 tapers from thefirst coil outer diameter to the second coil outer diameter.

In other examples in which inner liner 18 also tapers from a first outer(and/or inner) diameter to a second outer (and/or inner) diameter(smaller than the first outer (and/or inner) diameter), examples inwhich catheter body 12 tapers from a first outer diameter to a secondouter diameter, or both, structural support member 20 may taper tofollow the change in the outer diameter of inner liner 18, catheter body12, or both inner liner 18 and catheter body 12.

In some examples, at least two outer jacket segments 60 have differentthicknesses or diameters. For example, a lower diameter portion ofstructural support member 20, such as a smaller diameter distal section,may have increased flexibility and may enable a thicker outer jackethaving a lower durometer, and therefore more flexible, material, whilealso enabling the catheter to maintain a relatively constant innerdiameter of inner liner 18 and outer diameter of outer jacket 24.

In some examples, such as examples in which structural support member 20decreases in outer diameter (e.g., tapers) from proximal end 12A towardsdistal end 12B as illustrated in FIG. 1, the thickness of each of outerjacket segments 60 may increase in a direction from a proximal end ofouter jacket 24 towards a distal end. For example, outer jacket 24 mayexpand from a first inner diameter to a second, larger inner diameter.In the example shown in FIGS. 5B and 5C, proximal outer jacket segment60A has a first jacket inner diameter and distal outer jacket segment60B has a second jacket inner diameter, such that outer jacket 24expands from the first jacket inner diameter to the second jacket innerdiameter. As a result, a thickness of proximal outer jacket segment 60Amay be less than a thickness of distal outer jacket segment 60B and athickness of proximal section 58A of support layer 22 may be greaterthan a thickness of distal section 58B of support layer 22.

In some examples, such as examples in which catheter body 12 tapers inouter diameter proximate to distal end 12B as shown in FIG. 1, thethickness of adjacent outer jacket segments 60 may decrease in adirection from the proximal end of outer jacket 24 towards the distalend. For example, a thickness of first outer jacket segment 60A may begreater than a thickness of second outer jacket segment 60B. In someexamples, at least two segments 60 may also define different innerdiameters than each other, where the inner diameter of a particularsegment 60 may be selected to accommodate the portion of catheter body12 in which a sleeve corresponding to the segment 60 is to bepositioned. In some examples, each segment 60 has the same wallthickness (measured in a direction orthogonal to longitudinal axis 16(FIG. 1). In other examples, the wall thicknesses of segments 60 maydiffer.

The catheters described herein can be formed using any suitabletechnique. FIGS. 6 and 7 are flow diagrams of example methods of formingany of catheter 10 of FIGS. 1 and 2, portion 30 of FIG. 3, portion 40 ofFIG. 4, and/or portion 50 of FIGS. 5A-5C. FIG. 6 is a flow diagram of anexample method of forming the catheters of FIGS. 1-5 having asurface-treated structural support member, and will be described withreference to catheter 10 of FIG. 1.

In accordance with the technique shown in FIG. 6, structural supportmember 20 is surface treated by at least applying a surface treatment toa surface of at least a portion of structural support member 20 toincrease adhesion of structural support member 20 to inner liner 18and/or outer jacket 24. In some examples, the surface treatment isapplied to the entire structural support member 20. In other examples,the surface treatment is applied to only a portion, such that otherportions of structural support member 20 remain untreated in the samemanner. As an example, in some instances, structural support member 20may be surface treated for contact with only one of inner liner 18 orouter jacket 24. In some examples, applying the surface treatmentincludes applying the surface treatment to an inner radial surface ofstructural support member 20 without substantially applying the surfacetreatment to an outer radial surface of structural support member 20,such that structural support member 20 may have increased adhesion toinner liner 18 or support layer 22 between inner liner 18 and structuralsupport member 20. For example, a surface treatment may be directed tothe inner radial surface of structural support member 20; while theremay be unintentional treatment of some surfaces of the outer radialsurface of structural support member 20 during this process, a majorityof the outer radial surface may remain untreated by the surfacetreatment.

In some examples, applying the surface treatment includes applying thesurface treatment to an outer radial surface of structural supportmember 20 without substantially applying the surface treatment to aninner radial surface of structural support member 20, such thatstructural support member 20 may have increased adhesion to outer jacket24 or support layer 22 between outer jacket 24 and structural supportmember 20.

In some examples, the surface treatment includes a physical treatment,alone or in combination with the other surface treatments describedherein. A physical treatment includes any treatment that may result inan increase in contact area of the surface of structural support member20 for bonding with inner layer 18, outer jacket 24, and/or supportlayer 22, or an increase in mechanical interlocking between the surfaceof structural support member 20 and inner liner 18, outer jacket 24,and/or support layer 22. For example, a physical treatment may increasea surface area or surface deviation (e.g., slope angle) of the surfaceof structural support member 20. A variety of physical treatments may beused including, but not limited to, mechanical roughening, laserroughening, abrasion, and the like.

In some examples, applying the surface treatment includes roughening thesurface of at least the portion of the structural support member toincrease a surface roughness of the surface. An increased surfaceroughness may be, for example, an increased contact area, contact slope,and/or fractality of the surface of structural support member 20 withinner liner 18, outer jacket 24, and/or support layer 22, therebyincreasing adhesion between structural support member 20 and inner liner18, outer jacket 24, and/or support layer 22. In some examples, thesurface of at least the portion of the structural support memberincludes a surface roughness greater than about [minimum surfaceroughness measurement].

In some examples, the surface treatment includes a chemical treatment,alone or in combination with the other surface treatments describedherein. A chemical treatment includes any treatment that may result inan increase in chemical bonding between structural support member 20 andinner liner 18, outer jacket 24, and/or support layer 22. For example, achemical treatment may increase a charge or reactivity of the surface ofstructural support member 20 to increase intermolecular forces betweenstructural support member 20 and inner liner 18, outer jacket 24, and/orsupport layer 22. A variety of chemical treatments may be usedincluding, but not limited to, alkaline treatment, acid treatment,ionization, protonation, deprotonation, electric field charge, and thelike.

In some examples, applying the surface treatment includes chemicallytreating the surface of at least the portion of structural supportmember 20 to increase a charge of the surface. An increased charge ofthe surface may be opposite to a charge of the inner liner, the outercoating, and/or the support layer, thereby increasing an electrostaticattraction between the structural support member and the inner liner,outer jacket, and/or support layer. For example, structural supportmember 20 may include a positive charge, while outer jacket 24 mayinclude a negative charge, such that structural support member 20 andouter jacket 24 may be electrostatically attracted to each other.

In some examples, applying the surface treatment includes chemicallytreating the surface of at least the portion of structural supportmember 20 to functionalize the surface with reactive moieties. Forexample, the surface of structural support member 20 may be reacted withan acid or base to create reactive moieties, such as amines, carboxylicacids, or other reactive groups configured to react with polymers. Innerliner 18, outer jacket 24, and/or support layer 22 may include polymersthat include various functional groups capable of reacting with thereactive moieties on structural support member 20. Reactive moieties onthe structural support layer may bond (e.g., covalently) with thefunctional groups of inner liner 18, outer jacket 24, and/or supportlayer 22. As a result, the surface of at least the portion of structuralsupport member 20 may be covalently bonded to at least one of innerliner 18 or outer jacket 24.

In some examples, the surface treatment may include a coating treatment,alone or in combination with the other surface treatments describedherein. The coating treatment can include, for example, coating thesurface of a portion of the structural support member with a functionallayer, such as a reactive layer with reactive moieties. Rather thanprovide surface properties through a direct surface treatment of thestructural support member, a functional layer may provide the roughness,charge, and/or reactive properties described above with respect to thephysical or chemical treatments. In some examples, applying the surfacetreatment includes coating the surface of at least the portion ofstructural support member 20 with a reactive layer with reactivemoieties. For example, the surface of the structural support member 20may include a polymer coating that includes reactive moieties configuredto react with functional groups of inner liner 18, outer jacket 24,and/or support layer 22, such that the coating may be covalently bondedto at least one of inner liner 18 or outer jacket 24.

In some examples, applying the surface treatment includes applying thesurface treatment to, or in various amounts at, particular portions ofstructural support member 20 to increase the adhesion between structuralsupport member 20 and inner liner 18 and/or outer jacket 24. Forexample, a surface of a first portion of structural support member 20,such as a more distal portion, may be surface treated and a surface of asecond portion of structural support member 20, such as a more proximalportion, may not be surface treated or can be treated in a differentway. As a result, the surface of the first portion of structural supportmember 20 may have different surface properties than the surface of thesecond portion of structural support member 20. In some examples, thesurface of the first portion of structural support member 20 may have afirst surface roughness and a surface of the second portion ofstructural support member 20 may have a second surface roughness that isless than the first surface roughness. In some examples, a shearstrength of the first portion is greater than at least 20% higher than ashear strength of the second portion.

In some examples, the surface treatment may be applied to one or moreportions of structural support member 20 that may be subject torelatively high deformation. For example, a first portion of structuralsupport member 20 near distal opening 13 may be adjacent to a relativelylow durometer section of outer jacket 24 that is more compressible.During navigation of catheter 10 through vasculature, the first portionmay experience a relatively high amount of deformation that may causedelamination or detachment of outer jacket 24 from structural supportmember 20. Thus, the first portion may include the surface treatment tohelp compensate for the stresses that may cause delamination ordetachment of outer jacket 24 from structural support member 20.

In some examples, the surface treatment may be applied to one or moreportions of structural support member 20 having a relatively highdensity. For example, a first portion of structural support member 20may have a relatively high coil pitch or pics per inch and a secondportion of structural support member 20 may have a relatively low coilpitch or pics per inch. Due to the higher coil pitch, inner liner 18 andouter jacket 24 may have lower inter-coil or inter-braid contact in thefirst portion than the second portion of structural support member 20.For example, during positioning of outer jacket 24 described below, thefirst portion of structural support member 20 may have reduced flow orreflow of an outer jacket material between structures (e.g., coils) ofstructural support member 20. This reduced flow of the outer jacketmaterial may result in reduced contact area between inner liner 18 andouter jacket 24 in the first section compared to the second section,whether directly (as in a tri-layer catheter configuration) or viasupport layer 22 (as in a quad-layer catheter configuration illustratedin FIG. 2).

For example, in the example of FIG. 2, structural support member 20 is acoiled structural support member, and may include a first portion havinga first coil pitch and a second portion having a second coil pitch thatis less than the first coil pitch. In some examples, applying thesurface treatment includes applying the surface treatment to a surfaceof the first portion of structural support member 20 and refraining fromapplying a surface treatment to a surface of the second portion ofstructural support member 20. For example, applying the surfacetreatment may include roughening a surface of the first portion ofstructural support member 20 without roughening a surface of the secondportion of structural support member 20. In some examples, applying thesurface treatment includes applying the surface treatment to a surfaceof the first portion of structural support member 20 and applying thesurface treatment to a surface of the second portion of structuralsupport member 20 to a lesser degree than the first portion ofstructural support member 20. For example, applying the surfacetreatment may include roughening a surface of the first portion ofstructural support member 20 to a first surface roughness and rougheninga surface of the second portion of structural support member 20 to asecond surface roughness that is less than the first surface roughness.As another example, applying the surface treatment may includechemically treating a surface of the first portion of the coiledstructural support member to a first charge and chemically treating asurface of the second portion of the coiled structural support member toa second charge that is less than the first charge.

In some examples, the surface treatment may be applied to one or moreportions of structural support member 20 having a relatively large inneror outer diameter. For example, a first portion of structural supportmember 20 may have a relatively small diameter and a second portion ofstructural support member 20 may have a relatively large diameter. Dueto the greater diameter in the second portion of structural supportmember 20, inner liner 18 and outer jacket 24 may have lower inter-coilor inter-braid contact area in the second portion than the first portionof structural support member 20.

At any time prior to positioning structural support member 20 over innerliner 18 (102), inner liner 18 may be positioned over a mandrel (notshown). In some examples, inner liner 18 may be positioned over themandrel by at least inserting the mandrel through an end of inner liner18. After positioning inner liner 18 over the mandrel, surface-treatedstructural support member 20 may be positioned over inner liner 18(102). In examples in which structural support member 20 includes a coilmember, the wire defining the coil member may be wound over an outersurface of inner liner 18 or pushed over inner liner 18. The coil membercan be, for example, a single coil member that is devoid of any joints.In some examples, the structural configuration of structural supportmember 20 may be at least partially defined as it is wound over innerliner 18 in some examples. For examples, a shape memory wire or astainless steel wire may be wound over inner liner 18 to define thedesired coil pitch, the desired diameter(s), the desired taper, thedesired length, or any combination thereof of member 20. The shapememory wire may then be heat set to define structural support member 20.

Structural support member 20 may be secured in place relative to innerliner 18 using any suitable technique. In some examples, outer jacket 24may at least partially secure structural support member 20 to innerliner 18. After structural support member 20 is positioned over innerliner 18 (102), outer jacket 24 is positioned over an outer surface ofstructural support member (104). During and/or after positioning outerjacket 24, material of outer jacket 24 may be flowed and/or reflowedbetween structures (e.g., coils or braids) of structural support member20, such that at least a portion of a volume between the structures ofstructural support member 20 may be filled with the material of outerjacket 24. In some instances, the material of outer jacket 24 maycontact inner liner 18 to form an interface between inner liner 18 andouter jacket 24. This interface may provide adhesion between inner liner18 and outer jacket 24, in addition to adhesion between structuralsupport member 20 and inner liner 18 or outer jacket 24. Regardless ofwhether inner liner 18 and outer jacket 24 form an interface, outerjacket 24 may provide longitudinal support for structural support member20, such that outer jacket 24 may at least partially limit movement ofstructural support member 20 between inner liner 18 and outer jacket 24.In this way, outer jacket 24 may assist in integrating structuralsupport member 20 into catheter body 12.

In some examples, an adhesive and/or a polymer, such as support layer22, may be used to secure structural support member 20 to inner liner18. As noted above, in some examples, catheter body 12 includes supportlayer 22. To form support layer 22, a layer of a thermoplastic or athermoset polymer may be applied over structural support member 20 afterstructural support member 20 is positioned over inner liner 18 (102),while in other examples, a layer of a thermoplastic or a thermosetpolymer may be applied over inner liner 18 prior to positioningstructural support member 20 over inner liner 18. The thermoset polymermay be, for example, a viscoelastic thermoset polyurethane (e.g.,Flexobond 430). At least some of the polymer may be positioned betweenthe turns of the wire defining member 20.

Positioning the thermoset polymer over inner liner 18 and structuralsupport member 20 in this manner may help bond inner liner 18 andstructural support member 20 to outer jacket 24 through support layer22. For example, the polymer may contact surfaces of structural supportmember 20, including surfaces of structural support member 20 having asurface treatment, and provide a surface for bonding to outer jacket 24.In contrast, depositing a polymer over inner liner 18 prior topositioning structural support member 20 may lead to surfaces ofstructural support member 20 void of the polymer, where such surfacesmay not as readily or strongly bond with outer jacket 24 as surfaces ofsupport layer 22. After the polymer is positioned over inner liner 18and structural support member 20 (not shown), the polymer is cured (notshown), e.g., by heating and/or time-curing. In other examples, thepolymer can be cured after outer jacket 24 is positioned over innerliner 18, structural support member 20, and the polymer.

Outer jacket 24 may then be positioned over inner liner 18, structuralsupport member 20, and support layer 22(104). In some examples, outerjacket 24 is adhered to an outer surface of structural support member20, e.g., an adhesive and/or a polymer may be applied to outer surfaceof member 20 prior to positioning outer jacket 24 over member 20 andthen cured after outer jacket 24 is positioned over member 20. Inaddition to, or instead of, the adhesive, outer jacket 24 may be heatshrunk over member 20 and inner liner 18. In some examples, the heatshrinking of outer jacket 24 helps secure member 20 in place relative toinner liner 18.

In some examples, inner liner 18, outer jacket 24, and/or support layer22 may directly physically interact with the surface-treated structuralsupport member 20. As one example, structural support member 20 may haveincreased friction and/or bonding surface with inner liner 18, outerjacket 24, and/or support layer 22. An increased surface roughness mayincrease contact area, contact slope, and/or fractality of the surfaceof structural support member 20 with inner liner 18, outer jacket 24,and/or support layer 22, thereby increasing adhesion between structuralsupport member 20 and inner liner 18, outer jacket 24, and/or supportlayer 22. As another example, structural support member 20 may haveincreased mechanical interlocking with outer jacket 24 and/or supportlayer 22. For example, a material of outer jacket 24 and/or supportlayer 22 may flow or permeate into local deviations of the surface ofstructural support member 20 caused by increased roughness.

In some examples, inner liner 18, outer jacket 24, and/or support layer22 may chemically interact with the surface-treated structural supportmember 20. As one example, an increased charge of the surface ofstructural support member 20 may be opposite to a charge of inner liner18, outer jacket 24, and/or support layer 22, thereby increasing anelectrostatic attraction between structural support member 20 and innerliner 18, outer jacket 24, and/or support layer 22. As another example,inner liner 18, outer jacket 24, and/or support layer 22 may includepolymers that include various functional groups capable of reacting withthe reactive moieties on structural support member 20. Reactive moietieson structural support member 20 may bond (e.g., covalently) with thefunctional groups of inner liner 18, outer jacket 24, and/or supportlayer 22, such that the surface of at least the portion of structuralsupport member 20 may be covalently bonded to at least one of innerliner 18 or outer jacket 24.

FIG. 7 is a flow diagram of an example method of forming the cathetersof FIGS. 1-5 including an outer jacket having a plurality of outerjacket segments, and will be described with reference to portion 30 ofcatheter body 12 of FIG. 3. In accordance with the technique shown inFIG. 7, structural support member 20 may be positioned over inner liner18 (102), as described above with respect to FIG. 6.

Structural support member 20 includes one or more relatively highdensity sections interspersed with relatively low density sections. Inthe example of FIG. 3, first section 36A of structural support member 20has a first density, second section 36B of structural support member 20has a second density, and third section 36C of structural support member20 has a third density, such that the second density of second section36B is higher than the first and third densities of first section 36Aand third section 36C, respectively.

In some examples, the structural configuration of structural supportmember 20 may be at least partially defined prior to being positionedover inner liner 18. For example, a shape memory wire (e.g., anickel-titanium wire) or a wire of an otherwise heat-settable metal oralloy may be wound over a different mandrel (e.g., a “coil mandrel”) onwhich inner liner 18 is not present or over the mandrel (e.g., beforeinner liner 18 is positioned on the mandrel) to define at least one ofthe desired coil pitch, the desired coil diameter, the desired taperingprofile (e.g., a continuous tapering or progressive tapering), or thedesired length of structural support member 20, and then heat set tosubstantially hold its shape. The wire may then be subsequently unwoundfrom the mandrel onto a reel or a bobbin, and then positioned over innerliner 18. Structural support member 20 may be positioned over innerliner 18 by, for example, winding member 20 over inner liner 18 (e.g.,winding member 20 from the bobbin or reel onto inner liner 18) or bypushing inner member 20 over an end of inner liner 18.

In some examples, a wire formed from a shape memory metal/alloy or anotherwise heat-settable metal/alloy may be preformed into a helical coilhaving a constant pitch and the desired diameters, including the desiredtaper, and then, once positioned over inner liner 18, the layout of thecoiled wire may be adjusted to achieve the desired pitch profile (e.g.,the change in pitch over the length) of structural support member 20.For example, the pitch of the wire may be adjusted over inner liner 18to achieve the desired pitch profile. These adjustments may be mademanually, by hand, or by a computer-controlled device. In otherexamples, however, a wire may be preformed into a helical coil havingthe desired pitch profile and diameters for structural support member 20before being positioned over inner liner 18.

Defining some or all of the structural characteristics of structuralsupport member 20 prior to positioning member 20 over inner liner 18 mayhelp control the structural characteristics of structural support member20, as well as control the uniformity of the structural support member20 of multiple catheter bodies. Pre-shaping and shape-setting the member20 as a coil (as opposed to ordinary wire stock) causes the member 20 toconform closely to the inner liner 18 as the member 20 is wound onto theliner 18. This close conformance, on its own and in combination with theresulting reduced need for adhesives or other measures to keep the woundmember in place on the liner 18, helps reduce the wall thickness T inthe catheter body 12. In addition, shape-setting the structural supportmember 20 on a separate, heat-resistant mandrel enables the constructionof the catheter body 12 using the member 20 on a mandrel made of PTFE orother lubricious, non-heat resistant material.

After structural support member 20 is positioned over inner liner 18(102), outer jacket 24 is positioned over structural support member 20and inner liner 18 to form catheter body 12. Outer jacket 24 includes aplurality of outer jacket segments 34, such that positioning outerjacket 24 over structural support member 20 and inner liner 18 mayinclude positioning a plurality of sleeves around structural supportmember 20 and inner liner 18. For example, each sleeve may be slid overthe outer surface of member 20 and positioned longitudinally adjacent toat least one other sleeve. Each sleeve of the plurality of sleeves maycorrespond to one or more outer jacket segments 34.

The sleeves may have different compositions and/or properties. Forexample, at least two sleeves may have different materials, differentdurometers, and/or different thicknesses. In some examples, a sequencein which the sleeves may be positioned may define increasing ordecreasing flexibility of catheter body 12. As one example, to increaseflexibility from a proximal to a distal end of portion 30, a durometerof a first sleeve is greater than a durometer of the second sleeve, suchthat a durometer of first outer jacket segment 34A is greater than adurometer of second outer jacket segment 34B. As another example, todecrease flexibility from a proximal to a distal end of portion 30, adurometer of first sleeve is less than a durometer of the second sleeve,such that a durometer of first outer jacket segment 34A is less than adurometer of second outer jacket segment 34B.

In the example of FIG. 7, forming outer jacket 24 includes positioning afirst sleeve corresponding to first outer jacket segment 34A overstructural support member 20 (110) and positioning a second sleevecorresponding to second outer jacket segment 34B over structural supportmember 20, distal to the first sleeve (112). The first and secondsleeves may be positioned such that second section 36B of structuralsupport member 20 is longitudinally aligned with junction 32 betweenfirst outer jacket segment 34A and second outer jacket segment 34B. Uponfinishing construction of catheter body 12, structural support member 20will have a variable density that is higher near junction 32, therebyenforcing junction 32.

After positioning outer jacket segments 34, outer jacket segments 34 maybe mechanically connected together at junction 32 and configured tosubstantially conform to the outer surface of structural support member20, inner liner 18, and/or a support layer (not shown) using anysuitable technique. In some examples, segments 34 are formed from aflowable/reflowable material. Heat may be applied to segments 34 tocause at least a portion of segments 34 to melt and flow into spacesbetween structures of structural support member 20. The heat may causesegments 34 to at least partly fuse together to define a substantiallycontinuous outer jacket 24. The use of heat to apply outer jacket 24 tothe subassembly including inner liner 18 and structural support member20 may help eliminate the need for an adhesive and/or support layerbetween structural support member 20 and outer jacket 24.

In some examples, segments 34 are formed from a heat shrinkablematerial. A heat shrink tube may be positioned over segments 34, andheat may be applied to cause the heat shrink tube to wrap tightly aroundsegments 34. The heat and wrapping force may cause segments 34 to fusetogether to define a substantially continuous outer jacket 24. The heatshrunk tube may then be removed from the assembly, e.g., via skiving orany suitable technique. The use of heat shrinking to apply outer jacket24 to the subassembly including inner liner 18, a support layer(optional and not shown), and structural support member 20 may helpeliminate the need for an adhesive between structural support member 20and outer jacket 24. This may help minimize the wall thickness ofcatheter body 12 and, therefore, increase the inner diameter of catheterbody 12 for a given outer diameter. In addition, the absence of anadhesive layer adhering structural support member 20 to outer jacket 24may contribute to an increased flexibility of catheter body 12.

In some examples, as will be described with reference to FIG. 1 unlessotherwise indicated, a method of using catheter 10 includes introducingcatheter 10 into vasculature (e.g., an intracranial blood vessel) of apatient via an access point (e.g., a femoral artery or a radial artery),and guiding catheter body 12 through the vasculature. In some instances,catheter body 12 may encounter tortuous vasculature that exerts abending or compressive force on catheter body 12 in response to apushing or rotating force at a proximal end of catheter 10. As catheterbody 12 is advanced through the tortuous vasculature, catheter body 12may resist kinking or buckling. As one example, as illustrated in FIG.2, structural support member 20 may remain adhered to outer jacket 24and/or inner liner 12, at least partly due to increase adhesion from oneor more surface-treated surfaces of structural support member 20. Asanother example, as illustrated in portion 30 of FIG. 3, structuralsupport member 20 may support a junction 32 between segments 34 of outerjacket 24 to resist buckling near junction 32. As another example, asillustrated in portion 40 of FIG. 4, structural support member 20 mayprovide for greater variation in flexibility along catheter body 12. Asanother example, as illustrated in portion 50 of FIG. 5, outer jacket 24may provide for greater variation in flexibility and/or compressibilitywhile retaining a relatively constant inner and outer diameter ofcatheter body 12. In these various ways, catheter body 12 may beincrease flexibility and/or pushability of catheter 10 through tortuousvasculature of a patient. Any of the examples of catheter body 12characteristics that contribute to a resistance to kinking or bucklingcan be used in combination with each other.

Once distal end 12B of catheter body 12 is positioned at the targettissue site, which may be proximal to thromboembolic material (e.g., athrombus), the thromboembolic material be removed from the vasculaturevia catheter body 12. For example, the thromboembolic material may beaspirated from the vasculature by at least applying a vacuum force toinner lumen 26 of catheter body 12 via hub 14 (and/or proximal end 12A),which may cause the thromboembolic material to be introduced into innerlumen 26 via distal opening 13. Optionally, the vacuum or aspiration canbe continued to thereby draw the thromboembolic material proximallyalong the inner lumen 26, all or part of the way to the proximal end 12Aor hub 14. As a further option, the aspiration or vacuum may cause thethromboembolic material to attach or adhere to the distal tip; in such acase the catheter 10 or catheter body 12 and the thromboembolic materialcan be withdrawn from the vasculature together as a unit, for examplethrough another catheter that surrounds the catheter 10 or catheter body12.

As another example, the thromboembolic material may be removed from thevasculature using another technique, such as via an endovascularretrieval device delivered through the inner lumen 26 of the catheterbody 12. In such a method the catheter body 12 can be inserted into thevasculature (for example using any technique disclosed herein) and theretrieval device advanced through the inner lumen 26 (or through anothercatheter, such as a microcatheter, inserted into the vasculature throughthe inner lumen 26) so that the device engages the thromboembolicmaterial. The retrieval device and the material engaged thereby(together with any other catheter or microcatheter) can then beretracted into the inner lumen 26 and removed from the patient.Optionally, aspiration can be performed with or through the catheterbody 12 during retraction of the retrieval device and thromboembolicmaterial into the catheter body 12. The vasculature can comprise theneurovasculature, peripheral vasculature or cardiovasculature. Thethromboembolic material may be located using any suitable technique,such as fluoroscopy, intravascular ultrasound or carotid Doppler imagingtechniques.

Various aspects of the disclosure have been described. These and otheraspects are within the scope of the following claims.

What is claimed is:
 1. A catheter, comprising: an inner liner; an outer jacket; and a structural support member positioned between at least a portion of the inner liner and at least a portion of the outer jacket, wherein a surface of at least a portion of the structural support member is surface treated to increase an adhesion of the surface to at least one of the inner liner or the outer jacket.
 2. The catheter of claim 1, wherein the structural support member is surface treated on an inner radial surface of the structural support member without being surface treated on an outer radial surface of the structural support member.
 3. The catheter of claim 1, wherein the structural support member is surface treated on an outer radial surface of the structural support member without being surface treated on an inner radial surface of the structural support member.
 4. The catheter of claim 1, wherein the surface of at least the portion of the structural support member includes a surface roughness greater than about 2 microns Ra.
 5. The catheter of claim 1, wherein the surface of at least the portion of the structural support member is covalently bonded to at least one of the inner liner or the outer jacket.
 6. The catheter of claim 1, wherein the surface of at least the portion of the structural support member comprises a coating covalently bonded to at least one of the inner liner or the outer jacket.
 7. The catheter of claim 1, wherein the structural support member comprises a coiled structural support member.
 8. The catheter of claim 7, wherein a first portion of the coiled structural support member has a first coil pitch and a second portion of the coiled structural support member has a second coil pitch that is less than the first coil pitch.
 9. The catheter of claim 8, wherein the surface that is surface treated comprises a first surface of the first portion of the coiled structural support member, and wherein a second surface of the second portion of the coiled structural support member is not surface treated.
 10. The catheter of claim 8, wherein the surface that is surface treated comprises a first surface of the first portion of the coiled structural support member, the first surface having a first surface roughness, and wherein a second surface of the second portion of the coiled structural support member has a second surface roughness that is less than the first surface roughness.
 11. The catheter of claim 8, wherein a shear strength of the first portion is greater than about twice a shear strength of a structural support member that does not include the surface treatment.
 12. The catheter of claim 7, wherein a first portion of the coiled structural support member has a first diameter and a second portion of the coiled structural support member has a second diameter that is greater than the first diameter.
 13. The catheter of claim 1, wherein the structural support member comprises a braided structural support member.
 14. A catheter, comprising: an inner liner; an outer jacket; a support layer positioned between at least a portion of the inner liner and at least a portion of the outer jacket; and a structural support member positioned between at least a portion of the inner liner and at least a portion of the outer jacket, wherein a surface of at least a portion of the structural support member is surface treated to increase an adhesion of the surface to at least one of the inner liner, the outer jacket, or the support layer.
 15. The catheter of claim 14, wherein at least a portion of the support layer is positioned between the structural support member and the outer jacket.
 16. The catheter of claim 14, wherein the surface of at least the portion of the structural support member is covalently bonded to at least one of the inner liner, the outer jacket, or the support layer.
 17. The catheter of claim 14, wherein the surface of at least the portion of the structural support member comprises a coating covalently bonded to at least one of the inner liner, the outer jacket, or the support layer.
 18. The catheter of claim 14, wherein the structural support member comprises a coiled structural support member, and wherein a first portion of the coiled structural support member has a first coil pitch and a second portion of the coiled structural support member has a second coil pitch that is less than the first coil pitch.
 19. The catheter of claim 18, wherein the surface that is surface treated comprises a first surface of the first portion of the coiled structural support member, and wherein a second surface of the second portion of the coiled structural support member is not surface treated.
 20. The catheter of claim 18, wherein the surface that is surface treated comprises a first surface of the first portion of the coiled structural support member, the first surface having a first surface roughness, and wherein a second surface of the second portion of the coiled structural support member has a second surface roughness that is less than the first surface roughness. 